U.S. patent number 5,804,285 [Application Number 08/491,671] was granted by the patent office on 1998-09-08 for decorative sheet and method for producing the same.
This patent grant is currently assigned to Dai Nippon Printing Co., Ltd.. Invention is credited to Toshitake Kobayashi, Yoshiaki Netsu.
United States Patent |
5,804,285 |
Kobayashi , et al. |
September 8, 1998 |
Decorative sheet and method for producing the same
Abstract
A printed woodgrain pattern and a lustrous solid printed layer
are formed by printing on the back surface of a transparent
thermoplastic resin film to obtain a printed film. The printed film
and a colored thermoplastic resin film are superposed, the printed
film and the colored thermoplastic resin film are laminated to
obtain a laminated structure and, at the same time, the laminated
structure is embossed from the side of the colored thermoplastic
resin film by a doubling embossing method with an embossing die
provided with an embossing pattern of ridges and furrows to obtain
a decorative sheet. In the decorative sheet, a second and a third
embossed pattern each having a cross section having a smooth
outline expressed by a periodic function or a pseudoperiodic
function are formed in the interfaces between the colored
thermoplastic resin film and the lustrous printed layer and between
the lustrous printed layer and the transparent thermoplastic resin
film, respectively.
Inventors: |
Kobayashi; Toshitake (Tokyo-To,
JP), Netsu; Yoshiaki (Tokyo-To, JP) |
Assignee: |
Dai Nippon Printing Co., Ltd.
(JP)
|
Family
ID: |
15720976 |
Appl.
No.: |
08/491,671 |
Filed: |
June 19, 1995 |
Foreign Application Priority Data
|
|
|
|
|
Jun 21, 1994 [JP] |
|
|
6-160718 |
|
Current U.S.
Class: |
428/172; 156/277;
156/219; 156/196; 428/542.2; 428/207; 428/201; 428/167; 428/162;
428/161; 428/147; 428/143 |
Current CPC
Class: |
B32B
3/30 (20130101); B44C 1/24 (20130101); B44F
9/02 (20130101); B32B 38/06 (20130101); B32B
27/08 (20130101); B32B 27/20 (20130101); B41M
3/06 (20130101); B32B 2307/412 (20130101); Y10T
428/2457 (20150115); Y10T 156/1039 (20150115); Y10T
428/24521 (20150115); Y10T 428/24529 (20150115); Y10T
428/24612 (20150115); Y10T 428/24372 (20150115); Y10T
428/24405 (20150115); Y10T 156/1002 (20150115); Y10T
428/24901 (20150115); Y10T 428/24851 (20150115); B32B
2451/00 (20130101) |
Current International
Class: |
B32B
3/30 (20060101); B44C 1/00 (20060101); B41M
3/06 (20060101); B44F 9/00 (20060101); B44C
1/24 (20060101); B44F 9/02 (20060101); B41M
3/00 (20060101); B32B 003/00 (); B32B 031/00 () |
Field of
Search: |
;428/156,172,207,161,162,163,167,141,143,147,201,542.2
;156/279,196,219,228 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
4-64443 |
|
Feb 1992 |
|
JP |
|
2229965 |
|
Oct 1990 |
|
GB |
|
Primary Examiner: Loney; Donald
Attorney, Agent or Firm: Parkhurst, Wendel & Burr,
L.L.P.
Claims
What is claimed is:
1. A decorative sheet, comprising:
a transparent thermoplastic resin film having a back surface
provided with a printed pictorial pattern;
a lustrous layer having a back surface, said lustrous layer being
formed on the back surface of the transparent thermoplastic resin
film; and
a colored thermoplastic resin film having a back surface, said
colored thermoplastic resin film being formed on the back surface
of the lustrous layer,
wherein a first, a second and a third embossed pattern are formed
in the back surface of the colored thermoplastic resin film, in an
interface between the colored thermoplastic resin film and the
lustrous layer, and in an interface between the lustrous layer and
the transparent thermoplastic resin film, respectively, and
wherein respective outlines of cross sections of the second and the
third embossed patterns formed respectively in the interface
between the colored thermoplastic resin film and the lustrous layer
and in the interface between the lustrous layer and the transparent
thermoplastic resin film are composed of smooth curves expressed by
periodic functions.
2. A decorative sheet according to claim 1, wherein
the respective cross sections of the second and the third embossed
patterns formed respectively in the interface between the colored
thermoplastic resin film and the lustrous layer and in the
interface between the lustrous layer and the transparent
thermoplastic resin film are substantially parallel to each
other.
3. A decorative sheet according to claim 2, wherein
the position of the first embossed pattern formed in the back
surface of the colored thermoplastic resin film corresponds to
those of the second and the third embossed patterns formed,
respectively, in the interface between the colored thermoplastic
resin film and the lustrous layer and in the interface between the
lustrous layer and the transparent thermoplastic resin layer.
4. A decorative sheet according to claim 3, wherein
the first embossed pattern formed in the back surface of the
colored thermoplastic resin film comprises curved protrusions, and
curved depressions formed between the adjacent curved protrusions,
and wherein
respective cross sections of the protrusions and depressions are
rectangular.
5. A decorative sheet according to claim 1, further comprising
an overcoat coating an exposed surface of the transparent
thermoplastic resin film.
6. A decorative sheet according to claim 5, further comprising
an ultraviolet cured resin layer coating an exposed surface of the
overcoat.
7. A decorative sheet according to claim 1, wherein
each of the first, the second and the third embossed patterns is
composed of an arrangement of at least one of parallel curves and
parallel straight lines.
8. A decorative sheet according to claim 1, wherein
said first embossed pattern has protrusions and depressions, and
wherein
said lustrous layer includes a lustrous pigment having a denser
dispersion ratio at a portion of said lustrous layer corresponding
to said protrusions, and a sparser dispersion ratio at a portion of
said lustrous layer corresponding to said depressions.
9. A decorative sheet producing method, comprising the steps
of:
sequentially forming a printed pictorial pattern and a bright layer
on a back surface of a transparent thermoplastic resin film;
superposing a colored thermoplastic resin film on an exposed
surface of the bright layer; and
simultaneously forming a first embossed pattern in an exposed
surface of the colored thermoplastic resin film, and second and
third embossed patterns, each having a cross section having a
smooth curved outline expressed by a periodic function, in the
interfaces between the colored thermoplastic resin film and the
bright layer and between the bright layer and the transparent
thermoplastic resin film, respectively, with an embossing die
plate.
10. A decorative sheet producing method according to claim 9,
wherein
the step of superposing the colored thermoplastic resin film on the
exposed surface of the bright layer, and the step of forming the
first, the second and the third embossed patterns are carried out
substantially simultaneously.
11. A decorative sheet producing method according to claim 9,
wherein
the embossing die plate is provided with a pattern of alternative
ridges and furrows each having rectangular cross sections.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a decorative sheet having a solid
appearance resembling that of natural wood or fabric and embossed
woodgrain or fabric texture surfaces showing an improved lustrous
pattern that varies depending on its orientation relative to a
light source or direction of view, and a method for producing the
same.
2. Description of the Related Art
Embossing a decorative sheet to improve the ornamental appearance
of the decorative sheet has been generally practiced. An embossed
thermoplastic resin sheet is one of such embossed decorative
sheets. In one form of a decorative sheet fabricating method
disclosed in Japanese Patent Laid-open (Kokai) No. 4-64443, a
lustrous, solid printed layer and a printed pattern layer are
formed in that order on a colored polyvinyl chloride film, a
protrusions and depressions pattern of hair lines and curved lines
is embossed on the coated surface of the colored polyvinyl chloride
film, and then the embossed surface is coated with a transparent
thermoplastic resin film by dry lamination or with a transparent
paint coating to complete a decorative sheet. In another form of
this prior art decorative sheet producing method, a pattern layer
and a lustrous solid printed layer are formed on a back surface of
a transparent thermoplastic resin film and the transparent
thermoplastic resin film is embossed.
A decorative sheet producing method disclosed in Japanese Patent
Laid-open (Kokai) No. 3-8477 forms a printed woodgrain layer, a
lustrous solid printed layer and a solid printed layer of a
covering colored ink on one surface, on which a raised protrusions
and depressions pattern of wavy lines is formed, of a transparent
base sheet to produce a luster inherent to a woodgrain plate or
fabric texture.
The appearance of embossed decorative sheets is liable to be
spoiled by the deposition of dust and foreign matters in
depressions formed in the embossed surface and there is the
possibility that the raised patterns are abraded or damaged.
The design of a decorative sheet produced by coating the surface of
a colored polyvinyl chloride film with a lustrous solid printed
layer and a printed pattern layer, embossing the coated surface of
the colored polyvinyl chloride film and coating the embossed
surface with a transparent thermoplastic resin film by dry
lamination or with a transparent paint coating does not have deep
appearance because the lustrous solid printed layer underlies the
printed pattern layer. Since the ridges and furrows of an embossing
die plate formed by an ordinary process, such as an engraving
process or an etching process, have each a cross section of an
outline having sharp corners, such as rectangular corners, the
protrusions and depressions of the lustrous solid printed layer
that reflects light have rectangular cross sections and,
consequently, the luster of the decorative sheet is different from
that of natural wood or fabric and unsatisfactory.
SUMMARY OF THE INVENTION
The present invention has been made to solve those problems in the
prior art decorative sheet fabricating methods and it is therefore
an object of the present invention to provide an elegant woodgrain
decorative sheet of an excellent design, exhibiting a luster
resembling that of natural wood and having a realistic texture, and
a method for producing the same.
In a first aspect of the present invention, a decorative sheet
comprises a transparent thermoplastic resin film having a back
surface provided with a printed pictorial pattern, a lustrous layer
formed on a back surface of the transparent thermoplastic resin
film, and a colored thermoplastic resin film on a back surface of
the bright layer. In this decorative sheet, a first, a second and a
third embossed pattern are formed in a back surface of the colored
thermoplastic resin film, in a interface between the colored
thermoplastic resin film and the bright layer, and in an interface
between the bright layer and the transparent thermoplastic resin
film, respectively, respective outlines of cross sections of the
second and the third embossed pattern formed respectively in the
interface between the colored thermoplastic resin film and the
bright layer and in the interface between the bright layer and the
transparent thermoplastic resin film are composed of smooth curves
expressed by periodic functions or pseudoperiodic functions,
respectively.
In a second aspect of the present invention, a decorative sheet
producing method comprises the steps of sequentially forming a
printed pictorial pattern and a bright layer in this order on a
back surface of a transparent thermoplastic resin film, superposing
a colored thermoplastic resin film to a back surface of the bright
layer, and simultaneously forming a first embossed pattern in a
back surface of the colored thermoplastic resin film, and a second
and a third embossed pattern each having a cross section having a
smooth outline expressed by a periodic function or a pseudoperiodic
function in the interfaces between the colored thermoplastic resin
film and the bright layer and between the bright layer and the
transparent thermoplastic resin film, respectively, with an
embossing die (plate).
According to the present invention, a decorative sheet can have a
pattern of an excellent design and a deep luster resembling that of
natural wood or fabric and harmonious with the grain or fabric
texture, which are incomparable with those of the conventional
decorative sheets, and the lustrous regions move according to
orientation of the surface of the decorative sheet relative to a
light source or the direction of view providing the decorative
sheet with an elegant, realistic woodgrain or fabric texture
appearance.
The above and other objects, features and advantages of the present
invention will become more apparent from the following description
taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a decorative sheet in a first
embodiment according to the present invention;
FIG. 2 is a fragmentary sectional perspective view of a decorative
sheet provided with an overcoat in accordance with the present
invention;
FIG. 3 is a perspective view of an embossed pattern consisting of
parallel curves;
FIG. 4 is sectional view of a printed film and a colored
thermoplastic resin film;
FIG. 5 is an enlarged sectional view of an embossing die;
FIG. 6 is a typical sectional view of a printed film and a colored
thermoplastic resin film embossed with the embossing die of FIG.
5;
FIG. 7 is sectional view of a printed film embossed with the
embossing die of FIG. 5;
FIG. 8 is a plan view of a surface embossed with a pattern
consisting of sinusoidal lines;
FIGS. 9A, 9B, 9C, 9D, and 9E are plan views of embossed
patterns;
FIGS. 10A and 10B are diagrammatic views of a decorative sheet
producing method in accordance with the present invention and an
enlarged sectional view of an embossing mechanism shown in FIG.
10A, respectively;
FIG. 11 is sectional view of comparative examples of embossed
printed films; and
FIGS. 12A-12D are sectional views of the decorative sheet showing
distribution ratio of a lustrous pigment within a bright layer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a sectional view of a decorative sheet in a first
embodiment according to the present invention, FIG. 2 is a
sectional view of a decorative sheet in a second embodiment
according to the present invention produced by coating the surface
of the decorative sheet of FIG. 1 with a transparent resin layer to
improve abrasion resistance, chemical resistance and soil
resistance, FIG. 3 is a fragmentary sectional perspective view of
an embossed groove pattern consisting of parallel curves, FIG. 4(a)
is a sectional view of a printed film formed by printing a printed
woodgrain pattern and a lustrous solid printed layer on a
transparent thermoplastic resin film, FIG. 4(b) is a sectional view
of a colored thermoplastic resin film, FIG. 5 is a sectional view
of an embossing die provided with a pattern of alternate, parallel,
curved ridges and furrows, FIG. 6 is a typical sectional view of a
structure produced by laminating the transparent printed film of
FIG. 4(a) and the colored thermoplastic resin film of FIG. 4(b) by
doubling embossing using the embossing die of FIG. 5, FIG. 7(a) is
a sectional view of assistance in explaining an embossing process
for embossing a transparent thermoplastic resin film provided with
a printed woodgrain pattern and a printed lustrous solid printed
layer with the embossing die of FIG. 5, FIG. 7(b) is a sectional
view of an embossed pattern formed by the embossing process of FIG.
7(a), FIG. 8 is a plan view of a surface embossed with a pattern
consisting of sinusoidal lines, FIGS. 9A to 9E are pictorial views
of embossed patterns, FIG. 10A is a diagrammatic view of a
decorative sheet fabricating method in accordance with the present
invention, FIG. 10B is an enlarged sectional view of an embossing
mechanism shown in FIG. 10A, respectively, FIGS. 11(a) and 11(b)
are sectional views showing a comparative decorative sheet
fabricating method.
Referring to FIG. 1, an embossed decorative sheet in a preferred
embodiment according to the present invention comprises, as
principal components, a transparent thermoplastic resin film 11, a
printed woodgrain or fabric texture pattern 12, a lustrous solid
printed layer 13, and a colored thermoplastic resin film 3 provided
with a first embossed pattern 4a. A third embossed pattern 4c is
formed in a interface visible from the front surface, i.e. the
surface of the transparent thermoplastic resin film 11 on which the
lustrous solid printed layer 13 is formed, and a second embossed
pattern 4b is formed in the surface of the colored thermoplastic
resin film 3 joined to the lustrous solid printed layer 13.
The cross section of each of the second embossed pattern 4b and the
third embossed pattern 4c has a shape having rounded corners, and
the outline of the cross section is a smooth curved line expressed
by a periodic function or a pseudoperiodic function. There is no
particular restriction on the shapes of the outlines of the second
embossed pattern 4b and the third embossed pattern 4c. The outline
of the cross section of each of the second embossed pattern 4b and
the third embossed pattern 4c may be of a rounded rectangular pulse
train, a rounded triangular pulse train, a rounded trapezoidal
pulse train, a sinusoidal wave, a curve expressed by the Bessel
function, a cycloid curve, a curve expressed by an elliptic
function or a curve analogous with any one of those curves. A curve
expressed by a pseudoperiodic function as mentioned herein is
neither an accurately periodic curve nor a single-pulse curve, but
a curve with periods distributed in a certain range, apparently
analogous with a curve expressed by a periodic function, such as a
curve obtained by the amplitude modulation, frequency modulation or
phase modulation of a curve expressed by a periodic function or a
curve resembling a curve represented by a phonetic signal. When
need be, the surface of the transparent thermoplastic resin film 11
may be coated with an overcoat 14 and a UV-setting resin layer 15
as shown in FIG. 2 to enhance the abrasion resistance, chemical
resistance and soil resistance of the decorative sheet 1.
When producing the decorative sheet 1, a printed film 2 is prepared
by printing the printed woodgrain pattern 12 or a printed textural
pattern, and the lustrous solid printed layer 13 on the transparent
thermoplastic resin film 11.
Although it is possible to use an embossing die provided with
ridges and furrows undulating in, for example, a sinusoidal curve
and having a cross section with rounded corners for embossing and
laminating the printed film 2 and the colored thermoplastic resin
film 3, generally such an embossing die is difficult to make.
Therefore, an embossing die 5 having alternate parallel curved
ridges 6 and parallel curved furrows 7 as shown in FIG. 5, which is
easy to make, is employed. As shown in FIG. 6, the printed film 2
and the colored thermoplastic resin film 3 are put together, and
hot-pressed with the embossing die 5 on a press to laminate the
printed film 2 and the colored thermoplastic resin film 3 by fusion
and, at the same time, to form an embossed pattern by embossing the
printed film 2 and the colored thermoplastic resin film 3 from the
side of the colored thermoplastic resin film 3. The printed film 2
and the colored thermoplastic resin film 3 are compressed on the
press for a predetermined time, and then the thus laminated printed
film 2 and the colored thermoplastic resin film 3 are cooled to
complete the embossed decorative sheet 1.
It is desirable that the thickness of the colored thermoplastic
resin film 3 is in the range of one to five times the height of the
ridges 6, i.e., the depth of the furrows 7, to form the second
embossed pattern 4b and the third embossed pattern 4c, each having
rounded protrusions and depressions, in the interface between the
lustrous solid printed layer 13 and the colored thermoplastic resin
film 3, and in the interface between the transparent thermoplastic
resin film 11 and the lustrous solid printed layer 13,
respectively.
Since a structure formed by superposing the printed film 2 having
the the transparent thermoplastic resin 11, and the colored
thermoplastic resin film 3 having the aforesaid thickness is
embossed to produce the decorative sheet 1, the second embossed
pattern 4b and the third embossed pattern 4c formed in the
interface between the lustrous solid printed layer 13 and the
colored thermoplastic resin film 3, and in the interface between
the transparent thermoplastic resin film 11 of the printed film 2
and the lustrous solid printed layer 13, respectively, have each a
cross section having an outline of a smooth curve resembling a
rounded pulse train or expressed by a periodic function as shown in
FIG. 1. When the embossing die 5 having the pattern of the
rectangular ridges 6 and the rectangular furrows 7 as shown in FIG.
4 is used for embossing, the outer surface of the colored
thermoplastic resin film 3 is deformed in a pattern complementary
to the pattern of the embossing die 5, whereas the lustrous solid
printed layer 13 is deformed in a pattern having a cross section of
a smoothly undulating outline as shown in FIG. 6, because the
colored thermoplastic resin film 3 has the aforesaid thickness.
Thus, the second embossed pattern 4b formed in the interface
between the lustrous solid printed layer 13 and the colored
thermoplastic resin film 13 and the third embossed pattern 4c
formed in the interface between the transparent thermoplastic resin
film 11 and the lustrous solid printed layer 13 have each a cross
section having the smoothly curved outline as shown in FIG. 6.
As shown in FIG. 3, each of the first embossed pattern 4a and the
second embossed pattern 4b formed respectively in the opposite
surfaces of the colored thermoplastic resin film 3 of the
decorative sheet 1 consists of parallel curves, and the third
embossed pattern 4c, similarly to the first embossed pattern 4a and
the second embossed pattern 4b, consists of parallel curves. The
second protrusions and depressions embossed pattern 4b and the
third embossed pattern 4c defining the shape of the lustrous solid
printed layer 13 sandwiched between the transparent thermoplastic
resin film 11 and the colored thermoplastic resin film 3, and being
visible from the side of the transparent thermoplastic resin film
11 have each a cross section of a smoothly curved outline defined
by rounded protrusions and rounded rectangular depressions
expressed by a periodic function, as shown in FIG. 3.
If the printed film 2 provided with the printed woodgrain pattern
12 and the bright solid layer 13 is embossed without joining the
colored thermoplastic resin film 3 to the printed film 2, the
ridges of the embossing die 5 deforms the lustrous solid printed
layer 13 directly as shown in FIG. 7(a) and the very thin lustrous
solid printed layer 13 of 10 .mu.m or less in thickness forming the
embossed surface of the decorative sheet 1 is deformed so that the
lustrous solid printed layer 13 has a cross section having
alternate rectangular protrusions and rectangular depressions as
shown in FIG. 7(b). Thus, the lustrous solid printed layer 13 is
unable to exhibit the luster of natural wood faithfully because the
light reflecting mode of the embossed, lustrous solid printed layer
13 is different from that of the cell walls of natural wood.
The first embossed pattern 4a of protrusions and depressions formed
in the back surface of the colored thermoplastic resin film 3 is
formed by heating and pressing the superposed printed film 2 having
the transparent thermoplastic resin 11, and the colored
thermoplastic resin film 3 with the embossing die 5 having the
shape of a plate or a roll. The respective widths of the
protrusions 29 and the depressions 28 of the first embossed pattern
4a are in the range of 1 to 1000 .mu.m, more preferably, 60 to 100
.mu.m (FIGS. 1 and 2). The depressions 28 and the protrusions 29
may be the same or different from each other in width. The depth of
the furrows 28 is in the range of 5 to 100 .mu.m, more preferably,
20 to 35 .mu.m.
Generally, the first embossed pattern 4a, the second embossed
pattern 4b and the third embossed pattern 4c are formed by using
the embossing die 5 provided with a pattern of alternate furrows 8
and ridges 9 undulating in a plane in the shape of a sinusoidal
curve as shown in FIG. 8 to give the decorative sheet 1 a woodgrain
luster. However, embossing dies provided respectively with a
pattern of alternate parallel furrows and parallel ridges having
the shape of a curve 16, a pattern of alternate parallel furrows
and parallel ridges having the shape of a straight line 17 and a
pattern of alternate parallel furrows and parallel ridges having
the shape of a combination of the curve 16 and the straight line 17
may be used, as show in in FIGS. 9A-9E.
In the decorative sheet 1, the second embossed pattern 4b in the
interface between the lustrous solid printed layer 13 and the
colored thermoplastic resin film 3, and the third embossed pattern
4c in the interface between the transparent thermoplastic resin
film 11 and the lustrous solid printed layer 13 have each a cross
section having an outline defined by alternate protrusions having
rounded corners and depressions having rounded corners, expressed
by a periodic function or a pseudoperiodic function. Since the
protrusions and the depressions of the second embossed pattern 4b
and the third embossed pattern 4c are similar to the cell walls of
natural wood, the light scattering effect of the lustrous solid
printed layer 13 is similar to that of natural wood, and therefore,
the decorative sheet 1 has an elegant solid woodgrain appearance
and a luster resembling that of natural wood.
The embossing die 5 employed for producing the decorative sheet 1
must have a pattern of the parallel ridges 6 and the parallel
furrows 7. The embossing die 5 may have the shape of either a plate
or a roll. The ridges 6 and the furrows 7 may be formed by a known
engraving process or a known chemical etching process. The
respective widths of the ridges 6 and the furrows 7 may be in the
range of 1 to 1000 .mu.m, preferably, 60 to 100 .mu.m, more
preferably on the order of 80 .mu.m. The preferable depth of the
furrows 7 is in the range of 20 to 35 .mu.m. The respective widths
of the ridges 6 and the furrows 7 may be the same or different from
each other provided that the widths range between 60 and 100 .mu.m.
The ridges 6 of the embossing die 5, having a thickness less than
60 .mu.m are unable to form depressions having a depth large enough
to give an effective luster to the decorative sheet 1. The embossed
patterns 4a, 4b, 4c formed by using an embossing die having ridges
6 of a width not less than 100 .mu.m appears on the pictorial
pattern (printed woodgrain pattern) 12 of the decorative sheet 1 to
spoil the design of the decorative sheet 1.
When the respective widths of the ridges 6 and the furrows 7 are 80
.mu.m and the depth of the furrows 7 is 35 .mu.m, the depth of the
depressions 28 formed in the first embossed pattern 4a of the
decorative sheet 1 is 28 .mu.m, which is large enough to give an
effective luster to the decorative sheet 1. When the respective
widths of the ridges 6 and the furrows 7 of the embossing die 5
were 50 .mu.m and the depth of the furrow 7 was 35 .mu.m, the depth
of the depressions 28 formed in the first embossed pattern 4a of
the decorative sheet 1 was as small as 18 .mu.m, the depth of the
depressions in the second and third embossed patterns 4b, 4c was
less than 18 .mu.m, and the embossed patterns 4a, 4b, 4c was unable
to give an effective luster to the decorative sheet 1.
Generally, the transparent thermoplastic resin film 11 of the
decorative sheet 1 is a polyvinyl chloride film. An acrylic film, a
polyolefine film, a polyester film, a polyvinylidene chloride film,
a polystyrene film, a polycarbonate film, a polyvinyl alcohol film,
a polyamide film or such may be used as the transparent
thermoplastic resin film 11. The preferable thickness of the
transparent thermoplastic resin film is in the range of 50 to 200
.mu.m.
The colored thermoplastic resin film 3 is formed by extruding or
casting or other methods a thermoplastic resin containing a mixture
of titanium oxide powder, carbon black powder, red oxide powder, a
pigment, dyes and/or a filler in a film.
The thickness of the colored thermoplastic resin film 3, against
which the embossing die 5 is pressed directly, must be determined
so that the shapes of the ridges 6 having sharp edges and the
furrows 7 having sharp corners of the embossing die 5 are not
transferred faithfully to the printed film 2 and so that the
lustrous solid printed layer 13 in contact with the surface of the
colored thermoplastic resin film 3 is deformed to form the second
embossed pattern 4b of alternate protrusions having rounded edges
and depressions having rounded corners. The thickness of the
colored thermoplastic film 3 must be equal to or greater than the
height of the ridges 6, i.e., the depth of the furrows 7, of the
embossing die 5 not to transfer the shapes of the ridges and the
furrows of the embossing die 5 faithfully to the lustrous solid
printed layer 13, and it is preferable that the thickness of the
colored thermoplastic resin film 3 is five times or below the
height of the ridges 6, i.e., the depth of the furrows 7, of the
embossing die 5 to emboss the colored thermoplastic resin film 3
satisfactorily so that a luster resembling that of natural wood is
given to the decorative sheet 1.
A textural printed pattern may be used instead of the printed
woodgrain pattern 12. The printed woodgrain pattern 12 is formed by
gravure printing or the like. An ink for forming the printed
woodgrain pattern 12 by gravure printing is prepared by blending a
vehicle, such as a vinyl resin, an acrylic resin, a nitrocellulose
resin, an aminoalkyd resin, butiryl resin or the like, a pigment,
an ink and other necessary materials.
The lustrous solid printed layer 13 is formed by solid printing
using an ink containing a lustrous pigment 13a (FIG. 12). A bright
printed pattern layer or a metal thin film formed by vacuum
evaporation or sputtering may be used instead of the lustrous solid
printed layer 13. Generally, the lustrous pigment 13a is a mice
pigment produced by coating mica particles with titanium dioxide,
metal powder, such as aluminum powder, or pearl essence having a
pearly luster.
The overcoat 14 is formed to enhance the abrasion resistance, the
chemical resistance and the soil resistance of the decorative sheet
1. The overcoat 14 is formed of a transparent resin excellent in
abrasion resistance, chemical resistance and soil resistance,
generally, a polyurethane resin, by gravure printing or coating.
The suitable thickness of the overcoat 14 is in the range of 3 to 4
.mu.m. In some cases, the decorative sheet 1 is provided with a
ultraviolet cured (crosslinked or polymerized) acrylic resin layer
15 to enhance the scratch resistance thereof.
Next, the lustrous solid printed layer 13 is in detail described in
FIG. 12(a)-(d). The lustrous solid printed layer 13 is formed by
solid printing using the ink containing the lustrous pigment 13a
and a thermoplastic resin binder, as mentioned above.
In FIG. 12(a)-(d), when the printed film 2 and the colored
thermoplastic resin film 3 are laminated and embossed, the
dispersion ratio of the lustrous pigment 13a within the lustrous
solid printed layer 13 varies in accordance with the position of
the embossing die 5. As a result, the luster of the decorative
sheet 1 varies very much according to the orientation of the
surface of the decorative sheet 1 relative to the light source or
the direction of view, and therefore the luster of the decorative
sheet 1 can more precisely resemble that of natural wood or fabric
texture.
That is, first, the transparent thermoplastic resin film 1 having
the printed pictorial pattern 12, the lustrous solid printed layer
13, and the colored thermoplastic resin film 3 are superposed in
this order, heated and pressed by the embossing die 5 (embossing
plate) having the ridges 6 and the furrows 7 (FIG. 12(a)).
In this case, the lustrous solid printed layer 13 is strongly
pressed at the portion 30 thereof corresponding to the ridges 6,
and therefore the softened thermoplastic resin binder of the
portion 30 flows from the ridge side to the furrow side. With the
flow of the thermoplastic resin binder, the lustrous pigment 13a of
the lustrous solid printed layer 13 flows to the furrow side (FIG.
12(b) (c)).
As a result, the dispersion ratio of the lustrous pigment 13a
within the lustrous solid printed layer 13 becomes relatively low
(sparse) at the portion 30 of the layer 13 corresponding to the
ridges 6 (or to the depressions 28), while the dispersion ratio of
the lustrous pigment 13a becomes relatively high (dense) at the
portion of the layer 13 corresponding to the furrows 7 (or to the
protrusions 29).
Next, the embossing die 5 is removed from the colored thermoplastic
resin film 3 (FIG. 12(d)).
As the dispersion ratio of the lustrous pigment 13a within the
lustrous solid printed layer 13 is modulated in accordance with the
ridges 6 or the furrows 7 of the die 7 in this way, the luster of
the decorative sheet 1 which varies according to the orientation of
the surface relative to the light source or the direction of view,
becomes brighter at the portion 31 of the lustrous solid printed
layer 13 having the denser pigment 13a, and becomes darker at the
portion 30 of the lustrous solid printed layer 13 having the
sparser pigment 13a.
In addition, as the brightness of the luster of the decorative
sheet is effected not only by the dispersion ratio of the lustrous
pigment 13a but also by the second and third embossed patterns 4b,
4c having protrusions and depressions located according to the
dispersion ratio of the lustrous pigment 13a, the luster of the
decorative sheet can more effectively resemble that of the natural
wood because of the multiplier effect of the location of the
protrusions and depressions of the second and third embossed
patterns 4b, 4c, and the dispersion ratio of the lustrous pigment
13a.
Incidentally, polyvinyl acetate, vinyl chloride-vinyl-acetate
copolymer, polymethyl methacrylate, polybutyl methacrylate,
polymethyl acrylate, and polybutyl acrylate can be preferably used
as the thermoplastic resin binder of the lustrous solid printed
layer 13.
EXAMPLE
A printed film 2 as shown in FIG. 4(a) was made by forming a
printed woodgrain pattern 12, i.e., a pattern of the edge grain of
a Japanese cedar in this example, on the back surface of a 100
.mu.m thick polyvinyl chloride film (Riken Biniru K.K., 100 parts
by weight resin and 12 parts by weight plasticizer) by gravure
printing and forming a lustrous solid printed layer 13 over the
printed woodgrain pattern 12 by gravure printing using a gravure
provided with a depressed area of 60 .mu.m in depth and a bright
ink (Showa Inku K.K.) prepared by dispersing pearl essence produced
by coating mica particles of 15 .mu.m in average particle size with
titanium dioxide in an ink containing a binder prepared by mixing a
copolymer of vinyl chloride and vinyl acetate, and an acrylic
resin, and then the printed film 2 was taken up in a roll 21.
Then, as shown in FIG. 10A, the printed film 2 was unwound from the
roll 21, and a 60 .mu.m thick colored polyvinyl chloride film 3a
(Riken Biniru K.K., 100 parts by weight resin and 12 parts by
weight plasticizer) was unwound from a roll 22, the printed film 2
and the colored polyvinyl chloride film 3a were preheated with a
preheating rollers 26, the printed film 2 and the polyvinyl
chloride film 3a were laminated on a heating drum 23 into a
laminated sheet, and then the laminated sheet was embossed from the
side of the colored polyvinyl chloride film 3a with an embossing
roller 25 provided with an embossing pattern of sinusoidal ridges
and sinusoidal furrows, while the laminated sheet was heated at
160.degree. C., the embossing roller 25 was heated at a surface
temperature of 60.degree. C. and the laminated structure was fed at
a feed speed of 10 m/min. Thus, an embossed pattern was formed in
the colored polyvinyl chloride film 3a as shown in FIG. 10B to
obtain a decorative sheet 1. In the embossing roller 25, the width
of the sinusoidal furrows was 80 .mu.m, the width of the sinusoidal
ridges between the adjacent sinusoidal furrows was 80 .mu.m and the
depth of the sinusoidal furrows was 35 .mu.m. The shapes of the
respective cross sections of each ridge and each furrow of the
embossing roller 25 were rectangular.
The decorative sheet 1 thus produced had a cross section as shown
in FIG. 1. An overcoat 14 of an ink containing a two-component
polyurethane resin (OP-81, Showa Inku K.K.) was formed over the
transparent polyvinyl chloride film 11 of the decorative sheet 1 by
solid gravure printing. In some cases, a UV-setting resin layer 15
is formed over the surface of the overcoat 14 to enhance the
scratch resistance of the decorative sheet 1. In some cases, a
resin layer is formed between the lustrous solid printed layer 13
and the colored polyvinyl chloride resin film 3a to improve the
adhesion between the lustrous solid printed layer 13 and the
colored polyvinyl chloride resin film 3a.
In the decorative sheet 1 thus produced, a third embossed pattern
like the third embossed pattern 4c, and a second embossed pattern
like the second embossed pattern 4b were formed in the interface
between the transparent thermoplastic resin film 11 and the
lustrous solid printed layer 13 and in the interface between the
lustrous solid printed layer 13 and the colored thermoplastic resin
film 3, respectively. The embossed patterns 4b, 4c had each a cross
section consisting of alternate protrusions having rounded corners
and depressions having rounded corners like those shown in FIG. 1.
The decorative sheet 1 had a solid luster resembling that of
natural wood, and a realistic, elegant woodgrain appearance.
COMPARATIVE EXAMPLE
A printed film 2 having a lustrous solid printed layer 13 was
produced by the same process as that employed in producing the
printed film 2 of the example, and then 2 .mu.m thick brown solid
printed layer 18 was formed over the lustrous solid printed layer
13 by gravure printing. Then, the printed film 2 coated with the
brown solid printed layer 18 was embossed directly from the side of
the brown solid printed layer 18 to form an embossed pattern as
shown in FIG. 11(a) by the same process as that carried out in the
foregoing example and with an embossing die 5 provided with an
embossing pattern of sinusoidal ridges 6 and sinusoidal furrows 7,
which were the same in shape and dimensions as the embossing
pattern employed in the foregoing example. Embossed patterns formed
in the interfaces between the transparent thermoplastic resin film
11 and the lustrous solid printed layer 13 and between the lustrous
solid printed layer 13 and the brown solid printed layer 18 of a
decorative sheet 1 thus produced had each a cross section
consisting of alternate rectangular protrusions having edged
corners and rectangular depressions having edged corners as shown
in FIG. 11(b). The brightness of the surface of the decorative
sheet 1 was somewhat higher than that of natural wood and rather
unnatural, and the decorative sheet 1 had an insufficient
luster.
As is apparent from the foregoing description, the present
invention gives a decorative sheet an excellent design and a solid
luster comparable to that of natural wood, and provides a
decorative sheet having a realistic, elegant, woodgrain
appearance.
When the decorative sheet is provided with a sinusoidal embossed
pattern of sinusoidal waves extending along a direction
perpendicular to the orientation of the printed woodgrain pattern,
the luster varies according to the orientation of the surface of
the decorative sheet relative to the light source or the direction
of view.
Although the invention has been described in its preferred form
with a certain degree of particularity, obviously many changes and
variations are possible therein. It is therefore to be understood
that the present invention may be practiced otherwise than as
specifically described herein without departing from the scope and
spirit thereof.
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